Calls made by telephones and video telephones are controlled by a call-control system or telecommunication device control system that is usually referred to as a PBX. PBX stands for private branch exchange. While the control systems used by modern VOIP (voice over IP) telephone systems do not exchange anything the term PBX is still commonly used to describe the controllers that have the same core functionality of PBXs used in public switched telephone networks where the term originated.
Current wide-area telecommunications networks for Internet Protocol devices, broadly, have two different configurations or categories for their PBXs that are each described below.
One arrangement uses a PBX shared by a plurality of organisations that is in a single physical location; the plurality of organisations share the same PBX hardware. It is a so-called public network. A telecommunication network 8 incorporating such an arrangement is illustrated in FIG. 1. The telecommunication network of FIG. 1 includes a PBX 12 which offers service to two groups of telephones 11 and 13 via the internet 10. The groups of telephones 11,13 share the hardware resources of the PBX 12. The groups of telephones 11,13 connect to the telephony service (PBX) 12 via the Internet 10. One group of telephones 11 is owned by one organisation and the other group of telephones 13 is owned by another organisation. A call between telephones of the same group (either between telephones in the group of telephones 11 or between telephones in the group of telephones 13) will use the resources of the PBX 12 regardless of where the telephones are located on the globe.
In this type of arrangement, a provider (a PBX 12) may be based in one country and a customer (using telephones 11) may connect to them from anywhere in the world, but a call will be routed via the country of the provider regardless of the destination. As a result, calls may have high latency and data packets forming the telephone call are more at risk of congestion loss because of the large number of hops they need to travel. The further away from this physical location of the PBX the user's telephone is located, the more inefficient the communications and resource usage becomes.
The other current wide-area telecommunications networks for IP devices is a dedicated service for a single organisation spanning a wide area. These are privately owned global telephone systems or private networks which permit an employee to connect their IP phone to an organisation's network from whatever of the organisation's sites they are on. The components in different locations share a common authentication system and a common privately-owned wide-area network or virtual private network (VPN) and so components can be moved from one location to another and will use the local resources. A telecommunication network 18 incorporating such an arrangement is illustrated in FIG. 2.
FIG. 2 illustrates a single set of telephones for a single organisation split into two groups 23A, 23B. Some of these telephones 23A connect to one PBX 21 via the Internet 20 and some of these telephones 23B connect to another PBX 22 via the Internet 20 thus, between them the telephones 23A, 23B of one organisation connect to two PBXs. These PBXs, in the telecommunications network 18, form part of a distributed telecommunications network which is owned by a single organisation.
In the arrangement of FIG. 2, the telephones 23A,23B are each connected to the PBX 21 or 22 of their organisation that is located physically closest to them. If a telephone 23A,23B was moved so it was now closer to the other PBX, it attaches to the new local PBX and uses its resources without intervention from the user; it is transparent to the user and the user would receive the same service experience that they received in the old location.
The corporate telecommunications system or private network of FIG. 2 allows local connection to a user and routes calls more efficiently than in the public network example of FIG. 1. However, the networks and hardware of the arrangement of FIG. 2 is owned by a single organisation cannot be shared with other organisations.